DUBAI – Saudi Arabia has arrested 431 people suspected of belonging to Islamic State cells and thwarted attacks on mosques, security forces and a diplomatic mission, the interior ministry said on Saturday.

The announcement came after a car bomb exploded at a checkpoint near the kingdom’s highest security prison on Thursday, killing the driver and wounding two security officials in an attack claimed by Islamic State.

A string of deadly attacks carried out by followers of the ultra-hardline militant group based in Iraq and Syria has fueled concerns about a growing threat of militancy in the world’s top oil exporter.

“The number arrested to date is 431, most of them citizens, in addition to participants from other nationalities … six successive suicide operations which targeted mosques in the Eastern province on every Friday timed with assassinations of security men were thwarted,” the ministry statement posted on the official news agency SPA said.

“Terrorist plots to target a diplomatic mission, security and government facilities in Sharurah province and the assassination of security men were thwarted,” it said.

The ministry did not elaborate on when the men were detained, but previous announcements that scores of suspects have been arrested suggest it was over the course of months.

Their alleged offences cited by the ministry ranged from smuggling explosives, surveying potential attack sites, providing transport and material support to bombers, smuggling in explosives from abroad and manufacturing suicide vests.

Islamic State has called on supporters to carry out attacks in the kingdom and killed 25 people in two suicide bombings at Shi’ite Muslim mosques in the country’s east in May.

A Saudi man, reportedly aided by several other men from the kingdom, blew himself up in a Shi’ite mosque and killed 27 worshippers in June.

The group says its priority target is the Arabian peninsula and in particular Saudi Arabia, home of Islam’s holiest places, from where it plans to expel Shi’ite Muslims.

The interior ministry said the suspects arrested in the kingdom were carrying out “schemes directed from trouble spots abroad and are aimed at inciting sectarian strife and chaos.”

US Defense Secretary Ash Carter will travel next week to Saudi Arabia as part of the Obama administration’s efforts to convince skeptical allies in the region about the benefits of the Iran nuclear deal.

In an interview with the New York Times this week, President Obama urged America’s traditional Sunni allies in the Gulf to better embrace their Shi’ite citizens.

“My argument has been to my allies in the region, let’s stop giving Iran opportunities for mischief. Strengthen your own societies. Be inclusive,” Obama said. –Reuters